language arts
letter writing
research papers (unit studies)
writing and language
grammar
phonics
With language arts, I tend towards the whole language approach, with extra work on areas that I see are needing it.  This way personalises and streamlines my approach to language. With three daughters homeschooling, all at different levels, I find this works well for me.  I think it does pay, though, to be 'up' on the grammar and phonics they need to be  covering,  so that you can quickly and easily see where work is needed.

So, though I've used worksheets for extra work on various areas, I tend more to writing letters, creative writing, and gathering and writing information with regard to their unit studies. 

I am finding that education games (homemade and tailored to your own needs), are a great way to keep reviewing phonics and grammar, so am starting to use these regularly.
language arts games and ideas
spelling